PROJECT SUMMARY/ABSTRACT One of the primary risk factors for peripheral artery disease (PAD) is type 2 diabetes mellitus (DM); 20-30% of adults with DM have PAD. The combination of PAD and DM (PAD+DM) puts individuals at a greater risk of poor health outcomes, compared to either condition alone. This is particularly true in regard to cardiovascular conditions. In fact, the risk of mortality is two times higher in adults with PAD+DM than in those with PAD alone. While exercise has been shown to be an effective therapy for improving walking distance among adults with PAD, there are some individuals, particularly those with PAD+DM, who experience a blunted response to exercise therapy. It is not known whether an increase in sedentary time occurs with structured exercise therapy for PAD, and could, in part, explain why some individuals with PAD+DM do not experience the same benefits from structured exercise therapy as individuals without DM. The purpose of this pilot study is to determine if older adults with PAD, with and without DM, engaging in structured exercise therapy change their sedentary behavior and to determine the relationship between sedentary time, physical function, and quality of life, independent of physical activity. This study will use a prospective, pre-test post-test design and will include 50 older adults with PAD (25 with PAD+DM, 25 with PAD only) who are participating in a 12-week structured exercise therapy program. The aims of this study are to: 1) Evaluate the effect of structured exercise therapy on objectively measured, free-living sedentary time in older adults with PAD, with and without DM, and 2) Determine if changes in sedentary time in the first 6 weeks of structured exercise therapy are associated with changes observed from baseline to 12 weeks in peak walking distance, physical function, falls, and quality of life in patients with PAD, with and without DM. At the completion of this study, we expect to have determined the variability, magnitude, and direction of change in sedentary time in older adults with PAD participating in structured exercise therapy and determined if the magnitude of change in sedentary time differs among older adults with PAD, with and without DM. We also expect to have determined if decreases in sedentary time are associated with improvements in peak walking distance, physical function, and quality of life and a reduction in falls, and if this relationship is independent of potential confounding variables (e.g., smoking, comorbidities, disease severity). The long-term goal of this research is to develop an intervention that can improve responsiveness to exercise interventions, reduce falls, and improve quality of life for older adults with PAD+DM. This study is significant because it could have a positive impact by helping older adults achieve optimal benefit from this method of self-management and reduce complications such as reduced physical function and decreased quality of life that are common in PAD. This improvement in quality of life and physical function could reduce morbidity and mortality, decrease health care costs, and help a growing population of older adults in the US with PAD enjoy greater health and wellbeing.